Added commands to add or remove mobs from blacklist.

/spf addmob [ENTITY_TYPE]

/spf removemob [ENTITY_TYPE]


Any changes made via these commands are automatically saved in config.yml


Known issues:
The addmob command cant recognize if the mon you are adding is a valid mob or not.
If you have multiple instances of the same mob in config.yml the removemob command will only remove it once.